/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.activiti.explorer.util;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.*;
import java.util.Map.Entry;

/**
 * @author 'Frederik Heremans'
 */
public class UriUtility {

    private static final String PARAMETER_SEPARATOR = "&";
    private static final String QUERY_STRING_SEPARATOR = "?";
    private static final String NAME_VALUE_SEPARATOR = "=";
    private static final String URL_PART_SEPARATOR = "/";

    /**
     * Get path fragments. eg: "/task/inbox/123" will return a list with three
     * values: "task", "inbox" and "123" in that order.
     */
    public static List<String> getFragmentParts(String url) {
        if (url != null) {
            List<String> parts = new ArrayList<String>();
            String[] partsArray = url.split(URL_PART_SEPARATOR);
            for (String part : partsArray) {
                if (part.length() > 0) {
                    parts.add(part);
                }
            }
            return parts;
        }
        return null;
    }

    /**
     * Extracts the query parameters from the given url fragment.
     */
    public static String extractQueryString(String fragment) {
        if (fragment != null) {
            int firstIndex = fragment.indexOf(QUERY_STRING_SEPARATOR);
            if (firstIndex >= 0) {
                return fragment.substring(firstIndex);
            }
        }
        return null;
    }

    /**
     * Extracts uri from the given url fragment, without the query params.
     */
    public static String extractUri(String fragment) {
        if (fragment != null) {
            int firstIndex = fragment.indexOf(QUERY_STRING_SEPARATOR);
            if (firstIndex >= 0) {
                return fragment.substring(0, firstIndex);
            } else {
                // No query string present, use full fragment
                return fragment;
            }
        }
        return null;
    }

    /**
     * Parses the parameters from the given url query string. When no encoding is
     * passed, default UTF-8 is used. Based on the implementation in Commons
     * httpclient UrlEncodedUtils.
     */
    public static Map<String, String> parseQueryParameters(String queryString, String encoding) {
        Map<String, String> parameters = new LinkedHashMap<String, String>();
        if (queryString != null) {
            // Remove '?' if present at beginning of query-string
            if (queryString.startsWith(QUERY_STRING_SEPARATOR)) {
                queryString = queryString.substring(1);
            }

            Scanner scanner = new Scanner(queryString);
            scanner.useDelimiter(PARAMETER_SEPARATOR);
            while (scanner.hasNext()) {
                final String[] nameValue = scanner.next().split(NAME_VALUE_SEPARATOR);
                if (nameValue.length == 0 || nameValue.length > 2)
                    throw new IllegalArgumentException("bad parameter");

                final String name = decode(nameValue[0], encoding);
                String value = null;
                if (nameValue.length == 2) {
                    value = decode(nameValue[1], encoding);
                }
                parameters.put(name, value);
            }
        }
        return parameters;
    }

    /**
     * Gets a valid query-string based on the given parameters.
     */
    public static String getQueryString(Map<String, String> parameters) {
        StringBuilder result = new StringBuilder();

        if (parameters != null) {
            for (Entry<String, String> param : parameters.entrySet()) {
                final String encodedName = encode(param.getKey(), null);
                final String value = param.getValue();
                final String encodedValue = value != null ? encode(value, null) : "";
                if (result.length() > 0) {
                    result.append(PARAMETER_SEPARATOR);
                } else {
                    result.append(QUERY_STRING_SEPARATOR);
                }
                result.append(encodedName);
                result.append(NAME_VALUE_SEPARATOR);
                result.append(encodedValue);
            }
        }

        return result.toString();
    }

    /**
     * Gets full path based on the given parts.
     */
    public static String getPath(List<String> parts) {
        if (parts != null) {
            StringBuilder result = new StringBuilder();
            for (String part : parts) {
                if (result.length() > 0) {
                    result.append(URL_PART_SEPARATOR);
                }
                result.append(part);
            }
            return result.toString();
        }
        return "";
    }

    private static String decode(final String content, final String encoding) {
        try {
            return URLDecoder.decode(content, encoding != null ? encoding : "UTF-8");
        } catch (UnsupportedEncodingException problem) {
            throw new IllegalArgumentException(problem);
        }
    }

    private static String encode(final String content, final String encoding) {
        try {
            return URLEncoder.encode(content, encoding != null ? encoding : "UTF-8");
        } catch (UnsupportedEncodingException problem) {
            throw new IllegalArgumentException(problem);
        }
    }
}